The proposed research will develop a methodological tool with which to investigate the possible perceptual underpinnings of attention. An effort will be made to measure the amounts of perceptual processing of stimuli from different sources in an attention task. A perceptual processing of stimuli from different sources in an attention task. A perceptual priming task will be superimposed on an attention task. Prime stimuli will be systematically issued from the different sources of stimuli comprising the attention task. The amount of perceptual processing of the prime stimuli (e.g., PICKAX) can be inferred from their effects on responses (e.g., free associations) to test stimuli (e.g., MINE). The test stimuli periodically interrupt the attention task at specific time intervals after the presentations of their prime stimuli.